The photoluminescence quenching of lightly doped p-type porous silicon in contact with aqueous acidic electrolytes is investigated under reverse-bias conditions. A complete and reversible quenching of the light emission is observed under infra-red illumination of the samples. This quenching is assigned to the injection into the porous layer of the electrons which are photogenerated in the substrate. The quenching features are studied as a function of the electron concentration in the porous layer, which is varied either by changing the intensity of the light excitation that generates the minority carriers in the silicon bulk or, at a given light intensity, by changing the electrolyte composition. In the latter case, the electron concentration is dependent on the electrochemical reactions which take place at the porous layer surface and which partly consume the injected electrons. It is shown that the amount of injected electrons directly determines the magnitude of the quenching and the associated spectral changes. It is concluded that the assumption of an enhanced charge carrier separation by the electric field as a possible quenching mechanism can be ruled out, and that the experimental results rather support the hypothesis that the quenching involves an Auger recombination process.
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